Along with enhancement in a definition of a display apparatus, further enhancement in an image quality of an image shot by using an image pickup apparatus (shot image) is desired. However, an optical degradation (blur) such as an aberration or a diffraction generated by an optical system in the image pickup apparatus is generated in the shot image. For this reason, information of an object space is lost, which leads to decrease in the image quality.
A large number of techniques for correcting the optical degradation (blur) of the shot image and obtaining an image having a still higher definition have been proposed up to now. PTL 1 proposes a technique for correcting the aberration by using a Wiener filter. Since the aberration changes depending on an image height, blur correction filters respectively set for a plurality of image heights are used. PTL 2 proposes a technique using a Richardson-Lucy (RL) method instead of the Wiener filter.